The invention relates to a method of increasing the separating efficiency in a cyclone separator and to a cyclone separator for separating particles having varying size.
The separating efficiency of a cyclone is highly dependent on the inlet velocity of the particles entering the cyclone and on the particle size of the particles. An increased inlet velocity gives a higher separating efficiency. Small particles are more difficult to separate than large particles. This is due to the fact that small particles have a low falling velocity and are drawn more easily with the gas stream into the vortex in the central part of the cyclone separator.
To increase the separating efficiency, the most obvious thing to do would be to increase the inlet velocity of the particles entering the cyclone. However in a plant of conventional design this results in:
1. the pressure drop increasing, and
2. the erosion rate of the envelope surface of the cyclone increasing. The erosion is caused mainly by the larger particles.
A pressure drop increase can often be accepted, but an increased erosion rate with increasing entry speed leads to a drastic reduction of the life of the cyclone which is unacceptable for commercial reasons. To keep the erosion rate to an acceptable level, a maximum inlet velocity of about 20-30 m/s is normally used.